I belong to several online groups specializing in collecting ancient coins. I and others on these groups have alerted Ebay numerous times about fakes that are being offered as genuine antiquities. On occasion, the auctions were killed. Most often, Ebay did nothing and did not even acknowledge my contact until after the auction was closed if at all. Ebay does not make this process easy, and I no longer bother flagging even the most blatant howlers. Ebay made it more difficult to detect bad sellers and alert unsuspecting bidders by permitting hidden feedback and limiting the number of feedbacks viewable. Now that Ebay has hidden bidders names it is no longer possible to alert unsuspecting bidders that they are about to be fleeced, sometimes for hundreds of dollars.
I think that there are likely other lawsuits waiting in the wings. Ebay would be better served taking the money it will spend on lawyers and settlements and do what is necessary to be more responsive to complaints and notifications of fraud.